Most commercially available automotive engines use fixed lift and duration intake and exhaust valve events. As a result, there is a compromise between the best fuel economy, emission control and engine power conditions.
Potentially better fuel economy, emission control and engine output benefits can be realized and particularly at part load conditions if the engine pumping losses are eliminated or minimized. This can be realized by using unthrottled operation coupled with a phase shifting of the intake valve event from a normal schedule to close within a range of either early or late in the engine cycle as a function of the mass of charge to be trapped, and heating the intake air to compensate for a reduction in compression end temperature that results from phase shifting of the intake valve.